Airless pump dispensers have become extremely popular for a variety of reasons. Since they operate under a vacuum, they are particularly useful in connection with certain personal care products and pharmaceutical products, particularly those which can be degraded upon contact with air. These airless pump dispensers have also become more of a standard for use in the total evacuation of viscous products from their containers. In the past these viscous products have been packaged in jars or flexible tubes. The airless pump dispensers are thus preferred over these products due to the elimination of contamination of the product by the need to put your hand in the jar, and in order to maintain dispensing, and to provide virtually total product evacuation as compared to flexible tubes for example. In addition, the airless pump dispensers have a minimal number of moving parts, and have become extremely efficient in their operation.
In connection with these devices and in order to maintain an air-free environment, these devices generally either include a collapsible bag containing the fluid or other product being dispensed, or they include a movable piston within the container, which moves upwardly in order to enclose the material being dispensed in a decreasing volume as the material is being dispensed.
Among the various airless pumps which are used in these dispensing devices, a number are well known in the art and are commonly available on a commercial basis. As examples, reference is made to U.S. Pat. Nos. 6,685,062; 7,891,522; 7,934,626; and 6,332,561, the disclosures of which, particularly relating to the airless pumps themselves, are incorporated herein by reference thereto.
As a particular example, reference is made to U.S. Pat. No. 6,685,062, the entire disclosure of which is incorporated herein by reference thereto. In particular, in referring to FIG. 1 herein (corresponding to FIG. 3 of the '062 patent), a preferred form of airless pump dispenser is shown. Thus, in this embodiment, a button 300 is vertically movable on the top of screw cap which is formed with a nozzle 400, a stent 600 connected to the lower part of button 300 communicating with the nozzle 400, a cylinder housing 1000 with a check valve 1400 in opening 1500 of the lower part of the housing. In this manner, when the button 300 is pressed, stem 600 is lowered along with piston 900 so that the contents of the cylinder housing 1000 are now put under pressure, and with the check valve 1400 closed. The contents of the cylinder housing 10′ are then ejected through the channel in the stent 600 and nozzle 400. That is, with the piston 900 lowered, the openings 1100 are exposed within the cylinder housing 1000, and the fluid can enter the channel in stent 600 therethrough. With spring 800 compressed, release of the button 300 causes stem 600 to be raised by spring 800 resulting in a vacuum or reduced pressure in the cylinder housing 1000 so that the check valve is open to draw contents into the cylinder housing 1000 from the lower chamber of the container. At the same time, since the piston 900 has risen, the openings 1100 are again covered by sealing member 1200, so that fluid can no longer enter the channel in the stent 600.
There are other types of dispensing devices which include spring mechanisms in the lower portion thereof. For example, U.S. Pat. No. 5,685,456 discloses a spray dispensing system for liquids or particulates in which the reservoir chamber includes a collapsible enclosure. Thus, a shaped memory component or spring at the bottom of the container maintains constant delivery pressure for that material. Thus, this does not utilize an airless pump system, and the spring 24 shown in FIG. 1 thereof is specifically intended to pressurize the system.
In addition, U.S. Pat. No. 4,938,393 discloses yet another dispensing system in which the dispensed material is maintained without leakage when the package is subjected to external forces. In this device the valve 30 is in a closed position to prevent leakage, and during use the valve is moved into a position as shown in FIG. 7 of this patent, for example. This dispenser thus includes a bottom piston 70 which follows removal of the material from the device. In order to eject the material a downward force F is applied to pressurize the material in the container body so that, once again, the container means in the follow-up piston are forced against the interior bore to dispense the material. Upon withdrawal of the pressurizing piston 80, a void is created beneath the piston which creates a suction, thereby lifting surface 76. Once again, this is not a typical airless pump system, and the bands 70 at the bottom of the device are critical in dispensing the material from the container.
A problem encountered with conventional airless pump devices is that in order to operate properly the package must be filled with little or no headspace. Having such a space disposed at the top of the container would cause the customer to have to prime the pump by stroking the pump several times until the product is forced up by the piston and dispensed therethrough. Thus, particularly in connection with water-based products being utilized in these dispensers, a problem is created if the product freezes, such as during shipment or delivery. This causes the product to expand, pushing the pump out of the container or causing the container to crack or rupture. Thus, one of the objects of this invention is to solve this problem and to do so without creating any headspace in the package, which again would require priming by the customer.